"Everything is going to be done to minimise the disruption to tourists and New Zealanders.
"One of the three unions has settled, so there is a core of specialist staff there."
Asked if temporary workers could be brought in from police and Customs to cover aviation security, Mr Key said, "potentially, yes".
The strikes would not shut any airport, but would cause considerable delays unless other measures were taken, the Prime Minister said.
Transport Minister Simon Bridges said since the collective agreement ended about a year ago.
"There have been strong offers by the Civil Aviation Authority. If you compare it across the public sector they can be seen at the upper end of the kind of offers we see in this area. What you are seeing here is a strike notice that is designed to cause maximum disruption. Our hope is still that we can mediate this and have an amicable solution so it doesn't get to the position of strike."
The vote to walk off the job came from workers yesterday after they failed to reach an agreement with the Aviation Security Service over pay rises and clawbacks in a new collective agreement.
The planned industrial action will affect the country's main domestic and international airports with three-hour strikes at Auckland and Wellington airports between July 20 and 27.
There will also be a ban on overtime and extra hours at those airports and at Christchurch Airport.
The striking staff work for the Aviation Security Service, which is part of the Civil Aviation Authority and contracts workers at airports around the country to screen passengers and carry out other surveillance services.
Up to 75 per cent of its staff are members of the E tu and Public Service Association (PSA) unions.
E tu aviation spokesman Kelvin Ellis said the workers didn't want to take the industrial action, the first in 30 years, but felt they had no other option after almost a year of negotiations.
"They've reached absolute frustration. They don't want to but they don't think they have any other choice. They've had enough."
Mr Ellis said the strikes would likely have a "significant impact" on screening times and may delay flights but he didn't think it would result in cancellations.
PSA national secretary, Glenn Barclay, said members were reluctant to take industrial action but felt they had no choice because the latest offer meant some would go three years without a pay rise.
Mr Barclay said the service had the money to make a better offer, as its annual report showed a surplus of $5.8 million in 2014-15.
"Aviation security workers are law enforcement officers, who help make New Zealand's aviation industry one of the safest and most highly regarded in the world."
The strikes could be prevented by the service making a "fair offer" that addressed their concerns and ensured they were fairly rewarded for the crucial job they did, Mr Barclay said.
Civil Aviation Authority spokesman Mike Richards said airport security would not be compromised by the strikes and contingency plans were in place. He hoped the issues could be resolved amicably.
Labour leader Andrew Little said the Government's threat to bring in police or Customs was "good old-fashioned National union-bashing".
Aviation security was an increasingly important role, he said, and airport staff were under growing pressure because of global security threats.
As a result, the Government needed to make a reasonable settlement with the sector, Mr Little said.
"The Government has to make sure we have an aviation security service that is up for the job, good professional people, and does its job of keeping our airports safe and secure."
Mr Little said union members did not take industrial action lightly, and they were responding to years of low pay increases and the rising cost of living.
"You cannot continue to keep the lid on reasonable pay claims and expect that nothing is going to happen."
The Labour leader doubted that any strikes would damage New Zealand's economy, saying that the schedule for industrial action was just a few hours a day.
Strikes:
Auckland
• Wed July 20: 10am-1.30pm plus overtime/extra hours ban all day
• Mon July 25: 3.30pm-6.30pm 1830 plus overtime/extra hours ban all day
• Wed July 27: 5.30am-8.30am plus overtime/extra hours ban all day
Wellington
• Wed July 20: 10am-1.30pm plus overtime/extra hours ban all day
• Fri July 22: 3.30pm-6.30pm plus overtime/extra hours ban all day
• Tues July 26: 5.30am-8.30am plus overtime/extra hours ban all day
Christchurch
• Wed July 20: overtime/extra hours ban all day
• Mon July 25: overtime/extra hours ban all day
• Wed 27 July: overtime/extra hours ban all day
